Why Add Alternative Text Descriptions?

“Alt text” is added to an image to provide a textual alternative to visual information. It is important to remember that some users won’t see your information, they’ll hear it!

According to the principles of Universal Design for Learning, information—including images—should be understandable in multiple ways. By adding an alt text to an image, you make its meaning available to people who, for whatever reason, cannot see it. Whether due to technological limitations or visual impairment, many people require a text alternative to visual information.

To add an alternative text description to an image, follow these steps:

Select the image (either click on the image or use the keyboard).

Open the context menu using one of the following methods:

Right-click (Windows) or Control-click (Mac) on the image.

Press the Context Key (Windows) while the image is selected.

Press Shift+F10 (Windows) while the image is selected.

Choose “Format Picture...” from the context menu (Figure 1).

Choose “Alt Text” from the left pane of the dialog box (Figure 2-a), and describe the image in the Description box (Figure 2-b). See “How to Describe an Image” in this tutorial.

Figure 1: Accessing alt Text in Microsoft PowerPoint 2010

To add alternative text to an image, choose Format Picture... from the context menu.

Figure 2: Adding/changing alt text in Microsoft PowerPoint 2010

Select “Alt Text” from the left-hand pane (a), and enter a meaningful description of the image in the “Description” box on the right (b).

How to Add Alternative Text to an Image (PowerPoint 2007)

(The following instructions apply to PowerPoint 2007 presentations saved in the .pptx file format, which debuted with that version of Office. Note that PowerPoint changes behavior when editing documents saved in the older .ppt format—see PowerPoint 2003 below.)

To add an alternative text description to an image, follow these steps:

Place the image in focus by either clicking on it or using the keyboard.

Pull up the context menu by pressing the Context Key, or by right clicking on the image.

Figure 3: Accessing Alternative Text through the Size and Position Dialog

Choose "Size and Position..." from the context menu.

Figure 4: Adding Alternative Text

Click on the "Alt Text" tab, then enter your description of the image.

How to Add Alternative Text to an Image (PowerPoint 2003)

The following instructions apply to PowerPoint 2003 presentations, as well as PowerPoint 2010 and 2007 presentations saved in the "PowerPoint 97-2003 presentations" or .ppt file format (also called Compatibility Mode).

To add an alternative text description to an image, follow these steps:

Double-click on the image to call up the Format Picture dialog box. (Alternative #1: Right-click on the image and select "Format Picture...." Alternative #2: Select the image and choose "Picture..." from the Format menu.)

Click on the "Web" tab, and locate the field labeled "Alternative text" (see Figure 5-a).

Enter an alternative text description of the image (Figure 5-b).

Figure 5: Adding Alternative Text

To add alternative text to an images, right-click on the object, choose Format > Picture, click on the “Web” tab, and enter a text description.

How to Describe an Image

Alternative text should describe the meaning of an image rather than its appearance. For example, instead of “Sign hanging on laboratory door,” tell the viewer what the image means: “Each laboratory has safety policies posted on the door.”

Keep descriptions as short as possible. It is generally unnecessary to begin a description with “photo of” or “picture of.” If describing a chart or graph, be as complete as possible.

In addition to alternative text, captions may be used to convey visual information to all users. Images can also be described in the text of your document.

Images without Significance

Before you describe an image, you should ask yourself whether it represents a meaningful piece of information or is merely “eye candy” adorning the page. If the image is simply decorative, a description is a waste of time. Such images are routinely skipped over by readers who can see them, and users of assistive technologies will want to do the same.

In HTML insignificant images are indicated by adding a “null” or “empty” alternative text attribute to the <img> tag, for example <img alt="">. In a PDF document, such images can be tagged as “artifacts.” Unfortunately, Microsoft Office offers no means of indicating that an image should be ignored, so it is best to simply leave decorative images alone. All other images should be described with alt text.

For more information about alternative text in HTML and Adobe PDF, see the following:

A Descriptive Text Tutorial Web Accessibility Tutorial for Creating Descriptive Text for Diagrams, Charts & Other Graphics from the Center on Education and Work from the University of Wisconsin-Madison.